Polymer electrolyte membrane fuel cell assemblies are relatively low temperature low operating pressure fuel cell assemblies that utilize a catalyzed polymer electrolyte membrane (PEM) to process air and a hydrogen-rich fuel to produce electricity and water. PEM fuel cells are well suited for use in mobile applications such as automobiles, buses, and the like, because they are relatively compact, light in weight and can be operated at essentially ambient pressure.
These types of fuel cells can be cooled by means of a water coolant which does not exit the cells in a liquid phase. During the cooling operation, water will pass from a coolant flow field through porous plate components of the cells and may pass through the electrolyte membrane where it will evaporate into the air stream in the active area of the cells. The water thus keeps the membranes moist and also cools the cells. During the cooling operation, small amounts of gases such as air and fuel can also pass through the porous plates into the coolant flow field. It is desirable to remove the diffused air and fuel from the water coolant so that the coolant will not be diluted and its cooling capability and its ability to prevent the porous bodies in the cell from drying will not be degraded. The air and fuel gas removal operation must be performed while preventing the coolant water from escaping from the coolant flow field.
We have devised a gas venting structure and method for effectively removing the air and fuel from the coolant while maintaining a proper exit pressure in the coolant flow field, and preventing the water coolant from escaping from the coolant flow field. Our structure and method also prevents coolant water or impurities therein from plugging or otherwise blocking the venting structure during operation of the power plant